Software Alternatives, Accelerators & Startups

Rainlendar VS ForthWrite

Compare Rainlendar VS ForthWrite and see what are their differences

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Rainlendar logo Rainlendar

Rainlendar - Customizable desktop calendar

ForthWrite logo ForthWrite

Email that sounds like you, and gets measurably more like you every week. Drafts in Gmail, Outlook, and the browser. Free to start.
Visit Website
  • Rainlendar Landing page
    Landing page //
    2023-04-21
  • ForthWrite Landing Page
    Landing Page //
    2026-06-19
  • ForthWrite Dashboard
    Dashboard //
    2026-06-19
  • ForthWrite In Gmail
    In Gmail //
    2026-06-19
  • ForthWrite Pricing
    Pricing //
    2026-06-19

ForthWrite is an AI email writing assistant for Gmail and Outlook that learns your writing style from your real sent mail. The more you use it, the more it sounds like you. Get smart drafts in seconds, auto-draft replies before you open your inbox, and maintain your personal voice at scale. Free to start, no credit card required. Works inside Gmail and Outlook on the web.

How it works

ForthWrite captures your tone, sentence rhythm, and sign-offs from your actual sent emails, then uses that profile to generate drafts that match how you write, not a generic AI voice. Every draft you edit or send improves the model over time.

Key features

  • Auto-draft: replies waiting in Gmail before you open your inbox
  • Voice matching from your real sent mail, not templates
  • Recipient-aware drafts that adapt to who you are emailing
  • Prompt Lab for version-controlling and A/B testing your persona prompt
  • BYOK support: bring your own API key for Claude, OpenAI, Grok, Mistral, and more
  • Works in Gmail and Outlook on the web, plus a standalone browser widget
  • Training data export and full data portability

Who uses it

Professionals who send high volumes of relationship-critical email: lawyers, financial advisors, recruiters, account executives, founders, and anyone who wants their inbox handled without sounding like a chatbot wrote it.

Pricing

Free tier includes 10 drafts per week with no credit card required. Paid plans start at $12/month and include unlimited drafts, custom persona prompts, and auto-draft.

Rainlendar

Pricing URL
-
$ Details
-
Platforms
-
Release Date
-

ForthWrite

$ Details
freemium $12.0 / Monthly (Standard plan)
Platforms
Web
Release Date
2026 June
Startup details
Country
United States
State
California
City
San Diego
Founder(s)
Curtis Boortz
Employees
1 - 9

Rainlendar features and specs

  • Customizable
    Rainlendar offers extensive customization options, including skins, themes, and layout adjustments, allowing users to tailor the calendar to their preferences.
  • Cross-Platform
    The application is available on multiple operating systems, including Windows, Mac OS X, and Linux, making it accessible to a broad range of users.
  • Lightweight
    Rainlendar is known for being a lightweight application that doesn't require significant system resources, ensuring smooth performance even on older machines.
  • Multiple Calendar Support
    Users can manage multiple calendars simultaneously, including events and tasks, with support for integration with other calendar services like Google Calendar.
  • Reminders and Alarms
    The application includes reminders and alarms to help users keep track of their important events and tasks.

Possible disadvantages of Rainlendar

  • Complexity
    The wide range of customization options may be overwhelming for new users, leading to a steeper learning curve compared to simpler calendar applications.
  • Limited Free Version
    Some advanced features are only available in the Pro version, requiring a purchase to unlock the full feature set.
  • User Interface
    While customizable, the user interface may appear outdated or less intuitive compared to more modern calendar applications.
  • Sync Issues
    Some users have reported occasional difficulties in syncing with online calendar services, leading to potential discrepancies in event data.
  • No Mobile App
    Rainlendar does not offer a mobile app version, which may limit accessibility for users who need calendar access on their smartphones or tablets.

ForthWrite features and specs

  • Voice Matching
    Learns from your real sent mail, not templates
  • Auto-draft replies
    Replies waiting in Gmail before you open your inbox
  • Batch-drafting
    Draft replies for your entire inbox with one click
  • Works in browser
    Gmail, Outlook, and web browsers
  • BYOK support
    Claude, OpenAI, Grok, Mistral, and more
  • Prompt Lab
    Version control and A/B test your persona prompt
  • Free tier
    10 drafts per week, no credit card required

Analysis of Rainlendar

Overall verdict

  • Rainlendar is considered a good choice for users looking for a lightweight yet powerful calendar application that offers extensive customization options. Its cross-platform support and integration with multiple calendar formats make it a versatile tool for personal and professional use.

Why this product is good

  • Rainlendar is a feature-rich calendar application that is known for its customizable interface, cross-platform compatibility, and support for various calendar formats such as iCalendar and Outlook. It offers extensive functionality including task management, alarms, and reminders. The ability to use skins allows users to personalize the look and feel according to their preferences.

Recommended for

  • Users who require a customizable and flexible calendar application.
  • Individuals looking for a cross-platform solution that works on Windows, macOS, and Linux.
  • Those who need a tool that can integrate multiple calendar formats like iCalendar and Outlook.

Analysis of ForthWrite

Overall verdict

  • I don't have verified information about a product called ForthWrite (forthwrite.ai). I cannot confirm its features, quality, or reputation, so I'm unable to provide an accurate assessment of whether it's good.

Why this product is good

  • No reliable data available on this specific product in my knowledge base
  • This may be a newer product, a niche tool, or possibly a fictional/hypothetical name
  • Providing details without verified information could result in inaccurate or fabricated claims

Recommended for

  • Unable to determine without verified product information
  • Consider checking the official website, user reviews on platforms like G2 or Trustpilot, and independent tech review sites for accurate details

Rainlendar videos

Desktopkalender kostenlos ! - Software Review Rainlendar - MrYouHelp

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ForthWrite videos

No ForthWrite videos yet. You could help us improve this page by suggesting one.

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Category Popularity

0-100% (relative to Rainlendar and ForthWrite)
Calendar
100 100%
0% 0
Email
67 67%
33% 33
Appointments and Scheduling
Email Productivity
0 0%
100% 100

Questions & Answers

As answered by people managing Rainlendar and ForthWrite.

Which are the primary technologies used for building your product?

ForthWrite's answer:

Next.js, React, Supabase, Anthropic Claude, OpenAI, Stripe, Vercel, Chrome Extensions API

What makes your product unique?

ForthWrite's answer:

ForthWrite learns your writing style from your actual sent mail, not a generic prompt. Every draft sounds like you wrote it because it was trained on how you actually write. It also auto-drafts replies before you open your inbox, so your email is partially handled before your day starts.

Why should a person choose your product over its competitors?

ForthWrite's answer:

Most AI email tools give you a blank box and a "write for me" button. ForthWrite builds a voice profile from your sent history and gets more accurate with every draft you edit or send. Unlike ChatGPT or Gemini, it works natively inside Gmail and Outlook with no copy-paste. Unlike Lavender, it writes the draft, not just scores it.

How would you describe the primary audience of your product?

ForthWrite's answer:

Professionals who send high volumes of relationship-critical email and cannot afford to sound generic: lawyers, financial advisors, recruiters, account executives, consultants, and founders managing their own inbox.

What's the story behind your product?

ForthWrite's answer:

Built out of frustration with AI writing tools that produce text that sounds nothing like the person sending it, and as a way to handle large amounts of daily email. The core insight was that your sent mail is the best training data you already have, and no tool was using it.

User comments

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Reviews

These are some of the external sources and on-site user reviews we've used to compare Rainlendar and ForthWrite

Rainlendar Reviews

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ForthWrite Reviews

  1. curtisboortz
    ยท Founder at ForthWrite ยท
    I built ForthWrite to fix generic AI email, and I still use it every day

    I built ForthWrite because I kept sending emails that sounded like they came from the same generic AI as everyone else. After launching it, I still use it for my own inbox every day, which is about the most honest endorsement I can give.

    The Chrome extension lives inside Gmail and Outlook on the web. Open a thread, hit Alt+Shift+D, and a draft comes back in your voice, not a template. The free tier is real: 10 drafts per week, no API key, no credit card. Voice matching is included on free, because that is the point.

    What keeps it useful compared to Gemini or a chat tab: it learns from what you actually send. Every edit you make before hitting send becomes a signal. Over time the drafts drift closer to how you really write, and the dashboard shows the improvement curve so you can see it happening.

    The web compose surface lets you draft from forthwrite.ai without installing anything, useful for people who want to try before committing to the extension.

    Standard adds recipient-aware and intent-aware drafting plus AI coaching. Pro adds auto-draft (replies waiting when you open Gmail), batch replies, and Prompt Lab for version-controlling your prompts. Teams adds a shared persona and seat-level analytics.

    ForthWrite is not for everyone. If you just need quick replies and tone does not matter, Gemini is free and already in your inbox. ForthWrite is for people where tone does matter: client communication, relationship-driven threads, external correspondence where sounding off costs something real.

    Disclosure: I am the founder and use it daily. Happy to answer questions in the comments.

    ๐Ÿ Competitors: Jace.ai, Fyxer, Mailmeteor
    ๐Ÿ‘ Pros:    Drafts land inside gmail and outlook; no copy-pasting from a chat window|Voice matching is on the free tier, not paywalled behind paid plans|No api key, no credit card to start; free tier runs on a server-side proxy|Learns from every edit you make before sending; drafts improve over time|Full keyboard flow: alt+shift+d to draft in any thread, no mouse required|Byok on paid plans, 9 providers supported, keys encrypted at rest|Web compose at forthwrite.ai works without installing the extension at all
    ๐Ÿ‘Ž Cons:    10 free drafts/week is enough to evaluate, not enough for a heavy inbox|Auto-draft, batch replies, and prompt lab all require the pro tier|Early-stage product; fewer third-party integrations than mature inbox tools|No mobile app: the extension and add-in are desktop-only (chrome on web, or the outlook desktop add-in)

What are some alternatives?

When comparing Rainlendar and ForthWrite, you can also consider the following products

Google Calendar - Spend less time managing your day & more time enjoying it

ReclaimAI - Helps users prioritize their work and personal calendars

Morgen.so - All-in-one Calendar, Tasks & Scheduler. Morgen is the single hub for everything that revolves around time management.

Superhuman - Superhuman is an email management tool.

Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.

Shortwave - Email smarter & faster with a reinvented experience for your Gmail